28 March 2013

Rubicon awarded patent for creating asymmetrical wafer configurations according to crystalline orientation

Rubicon Technology Inc of Bensenville, IL, USA, which makes monocrystalline sapphire substrates and products for the LED, RFIC, semiconductor and optical industries, says that the United States Patent and Trademark Office (USPTO) has granted a patent to Rubicon entitled, “Asymmetrical Wafer Configurations and Method for Creating the Same,” U.S. Patent No. 8,389,099.  The patent covers the creation of visual and tactile indicators to make sapphire wafers asymmetric according to their crystalline orientation, says the firm.

Sapphire wafers have specific orientation that is invisible to the naked eye. Rubicon has developed a process to make wafers appear asymmetrical via visual or tactile inspection. This is important as LED and semiconductor manufacturers process sapphire wafers using specific crystalline orientations. The patent helps manufacturers in the LED and SoS/RFIC industries eliminate costly and unnecessary steps to determine orientation of sapphire wafers during processing, such as x-ray crystallography.

“For Rubicon’s customers in the LED and SoS/RFIC markets, the crystal orientation is a critical factor in their manufacturing processes.  This patent provides a simple and elegant solution to eliminating costly mistakes in the processing of sapphire wafers,” said Raja M. Parvez, president and CEO of Rubicon Technology. 

Epitaxy-ready wafers have either an orientation flat or an orientation notch, but this provides insufficient information:  the wafer could be flipped front-to-back and still look the same yet be unusable in that state crystallographically. Only through repeated x-ray inspections could the manufacturer ensure that no wafers are reversed.  If the wafers are made asymmetrical, operators at each stage of production can verify surface orientation quickly and economically.

Rubicon’s patent demonstrates several different solutions for making sapphire wafers asymmetric. In one solution, a rounded corner on the orientation flat or notch allows a user to determine that the wafer has not been reversed.  In another solution, both corners of the flat are rounded to different radii.  These differences are enough to determine orientation by touch or visual inspection.  The technique can be applied to other substrates including silicon, silicon oxide, aluminum nitride, germanium, silicon carbide, gallium arsenide, gallium phosphide, gallium nitride, and amorphous analogs.

Tags: Rubicon Sapphire substrates

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